This invention relates to an image tube, which may be an image intensifier tube.
An image tube comprises an axially extending insulating tube or pipe having first and second open ends, a photoelectric cathode and a fluorescent anode sealed to the insulating tube to hermetically close in the first and second open ends, respectively, and an intermediate electrode in a hollow space enclosed with the insulating tube, the photoelectric cathode, and the fluorescent anode. The photoelectric cathode is for converting an input optical image projected thereon to a first electron image. In cooperation with the photoelectric cathode and the fluorescent anode, the intermediate electrode forms an electron lens in the hollow space for forming a second electron image on the fluorescent anode, which converts the second electron image to an output optical image. With a conventional image tube, background noise is unavoidably superposed on the output optical image. The background noise deteriorates the output optical image.